I collect all the boxes from scripts and other packaging. I love my medication boxes, because they are small and I end up with sets of boxes that can form books
the diagram above shows how I remove the ends of the boxes and flatten them to form a sleeve that I can put things in.
Above in this blurry photo (sorry), you can see some of the box sleeves and some tags which I cut from other card pieces. I must say that the surface of the packaging is usually a bit glossy, so I sand the surfaces and wipe them clean a little before applying the paint.
Above, you can see some of the texture I got on these surfaces with the sponge.
I will work more with these, so you will have to check back to see how little books evolve from these bits of painted card.
Happy creating!